SUBUNIT ORGANIZATION AND STRUCTURE OF LON PROTEASE

扫描电子显微镜(STEM)已被用来确定ATP依赖的蛋白酶LON的亚基组织。这种酶在原核生物和真核生物的有丝分裂过程中都起着重要的作用。LON由含有ATPase(A)和Protease(P)结构域的单一多肽链的多个拷贝组成。细菌的Lon序列与真核细胞的Lon有很强的同源性，已报道形成七聚体环。然而，对于细菌Lon，目前发表的数据并不是决定性的。暗场STEM测量表明，全长大肠杆菌Lon(野生型和Serala突变体)以及Lon-NA由十二聚体组成，而Lon-AP形成六聚体。通过与ClpAP蛋白酶复合体的ATPase组分ClpA的类比，Lon很可能由两个六聚体环组成。Lon-AP只形成六聚体的事实表明，N-末端结构域可能是全酶中两个六聚体环结合所必需的。-扫描电子显微镜，离子蛋白酶，亚基组织，结构，分子量

Scanning transmission electron microscopy (STEM) has been applied to determine the subunit organization of the ATP-dependent protease, Lon. This enzyme plays an important role in degrading misfolded proteins in prokaryotes as well as in the mitochrondria of eukaryotes. Lon consists of multiple copies of a single polypeptide chain that contains both the ATPase (A) and protease (P) domains. The sequence of bacterial Lon has a strong homology with eukaryotic Lon which has been reported to form heptameric rings. However, for bacterial Lon, currently published data are inconclusive. Dark-field STEM measurements show that full-length E. coli Lon (wild type and a ser-ala mutant) as well as Lon-NA are composed of dodecamers, whereas Lon-AP forms hexamers. By analogy with the protein ClpA which is the ATPase component of the ClpAP protease complex, it is likely that Lon is comprised of two hexameric rings. The fact that Lon-AP only forms hexamers suggests that the N-terminal domain may be required for association of two hexameric rings in the holoenzyme. - Scanning transmission electron microscopy, lon protease, subunit organization, structure, molecular weight